The pressure at which typical gas distribution systems supply gas may vary according to the demands placed on the system, the climate, the source of supply, and/or other factors. However, most end-user facilities equipped with gas appliances such as furnaces, ovens, etc., require the gas to be delivered in accordance with a predetermined pressure, and at or below a maximum capacity of a gas regulator. Therefore, gas regulators are implemented into these distribution systems to ensure that the delivered gas meets the requirements of the end-user facilities. Conventional gas regulators generally include a closed-loop control actuator for sensing and controlling the pressure of the delivered gas.
In addition to a closed loop control, some conventional gas regulators include a relief valve. The relief valve is adapted to provide over pressure protection when the regulator or some other component of the fluid distribution system fails, for example. Accordingly, in the event the delivery pressure rises above a predetermined threshold pressure, the relief valve opens to exhaust at least a portion of the gas to the atmosphere, thereby reducing the pressure in the system.
FIGS. 1 and 1A depict one conventional gas regulator 10. The regulator 10 generally comprises an actuator 12 and a regulator valve 14. The regulator valve 14 defines an inlet 16 for receiving gas from a gas distribution system, for example, and an outlet 18 for delivering gas to an end-user facility such as a factory, a restaurant, an apartment building, etc. having one or more appliances, for example. Additionally, the regulator valve 14 includes a valve port 36 disposed between the inlet and the outlet. Gas must pass through the valve port 36 to travel between the inlet 16 and the outlet 18 of the regulator valve 14.
FIG. 1A depicts the regulator valve 14 including the conventional valve port 36 of the regulator 10 in more detail. The conventional valve port 36 generally includes a one-piece valve port having an inlet 60, an outlet 62, and an elongated, generally cylindrical orifice 64 extending between the inlet 60 and the outlet 62. Gas must flow through the orifice 64 to flow through the regulator valve 14.
Still referring to FIG. 1A, the valve port 36 includes a body portion 66, a hexagonal nut portion 68, and a valve seat 70. The body portion 66 is generally circular in cross-section and includes a plurality of external threads 72 in threaded engagement with the regulator valve 14. The hexagonal nut portion 68 includes a hexagonal cross-section and is adapted to be engaged by a tool such as a pneumatic ratchet, for example, to install the valve port 36 into the regulator valve 14 or remove the valve port 36 from the regulator valve 14 to replace it with another valve port having an orifice of a different diameter to tailor the operational flow characteristics of the valve port to a particular application.
The valve seat 70 protrudes from the hexagonal nut portion 68 in a direction opposite from the body portion 68. The valve seat 70 includes a ring-shaped valve seat 70 having a generally tapered, triangular cross-section converging from the hexagonal nut portion and terminating at a seating edge 74. More particularly, the conventional valve seat 70 includes an inner surface 76 and an outer surface 78, which meet at the seating edge 74. The inner surface 76 is an extension of the orifice 64 in the valve body 36, and therefore has a diameter common with the diameter of the orifice 64. The outer surface 78 extends at an angle of approximately 45° relative to the inner surface 76. Thus, the outer surface 78 is generally frustoconical.
In the conventional valve port 36 depicted in FIG. 1A, the valve seat includes a seat height H and an orifice diameter D. However, as mentioned above, the valve port 36 may be replaced with another valve port having an orifice with a different diameter to tailor the operational characteristics of the regulator 10. Regardless of the diameter of orifice 64, the seat height H is constant for conventional valve ports.
Referring back to FIG. 1, the actuator 12 of the conventional regulator 10 is coupled to the regulator valve 14 to ensure that the pressure at the outlet 18 of the regulator valve 14, i.e., the outlet pressure, is in accordance with a desired outlet or control pressure. The actuator 12 is therefore in fluid communication with the regulator valve 14 via a valve mouth 34 and an actuator mouth 20. The actuator 12 includes a control assembly 22 for sensing and regulating the outlet pressure of the regulator valve 14.
The control assembly 22 includes a diaphragm 24, a piston 32, and a control arm 26 having a valve disc 28. The valve disc 28 includes a generally cylindrical body 25 and a sealing insert 29 fixed to the body 25. The body 25 may also include a circumferential flange 31 integrally formed therewith, as depicted in FIG. 1A. The diaphragm 24 senses the outlet pressure of the regulator valve 14. The control assembly 22 further includes a control spring 30 in engagement with a top-side of the diaphragm 24 to offset the sensed outlet pressure. Accordingly, the desired outlet pressure, which may also be referred to as the control pressure, is set by the selection of the control spring 30.
The diaphragm 24 is operably coupled to the control arm 26, and therefore, the valve disc 28 via the piston 32, controls the opening of the regulator valve 14 based on the sensed outlet pressure. For example, when an end user operates an appliance, such as a furnace, for example, that places a demand on the gas distribution system downstream of the regulator 10, the outlet flow increases, thereby decreasing the outlet pressure. Accordingly, the diaphragm 24 senses this decreased outlet pressure. This allows the control spring 30 to expand and move the piston 32 and the right-side of the control arm 26 downward, relative to the orientation of the regulator 10 of FIG. 1. This displacement of the control arm 26 moves the valve disc 28 away from the seating edge 74 of the valve seat 70 of the valve port 36, thereby opening the regulator valve 14. FIG. 1A depicts the valve disc 28 in a normal, open operating position. So configured, the appliance may draw gas through the orifice 64 in the valve port 36.
In the position depicted in FIG. 1A, the valve disc 28 is displaced away from the valve port 36 to allow gas to flow through the regulator valve 14 during normal operational conditions. Generally speaking, the exact position of the valve disc 28 is dependent upon a variety of factors, one of which may include the amount of gas flowing through the valve port 36, i.e., the flow capacity of the valve port 36, which is itself dependent on the diameter and volume of the orifice 64 in the valve port 36. For example, if the valve port 36 depicted in FIG. 1A were replaced with a valve port having a smaller orifice, and therefore, a smaller flow capacity, the valve disc 28 would position itself closer to the valve port 36. However, this balance does not always create optimum flow characteristics through the regulator valve 14.
For example, when valve ports with smaller diameters are utilized, the flow of gas through the regulator valve 14 tends to increase in velocity, while the volume of space immediately downstream of the valve port, i.e., between the valve port and the valve disc, is reduced. This reduced volume between the throat 11 and the valve disc 28 may detrimentally affect the efficiency at which the gas travels from the valve port 36 to the outlet 18 of the regulator valve 14. For example, the reduced volume may not provide sufficient space for high velocity gas flowing through the valve port 36 to efficiently recover and emerge through the outlet 18. In some circumstances, this can result in an increase in pressure at the outlet 18, thereby causing the diaphragm to sense an artificial increase in sensed outlet pressure and move the valve disc 28 toward the valve port 36 to reduce the amount of flow through the regulator valve 14. This coincidentally, reduces the outlet pressure to a pressure that is below the set control or desired outlet pressure. This phenomenon is known as “droop.” When “droop” occurs, the regulator 10 may not perform optimally.
In the conventional regulator 10 depicted in FIG. 1, the control assembly 22 further functions as a relief valve, as mentioned above. Specifically, the control assembly 22 also includes a relief spring 40 and a release valve 42. The diaphragm 24 includes an opening 44 through a central portion thereof and the piston 32 includes a sealing cup 38. The relief spring 40 is disposed between the piston 32 and the diaphragm 24 to bias the diaphragm 24 against the sealing cup 38 to close the opening 44, during normal operation. Upon the occurrence of a failure such as a break in the control arm 26, for example, the control assembly 22 is no longer in direct control of the valve disc 28 and inlet flow will move the valve disc 28 into an extreme open position. This allows a maximum amount of gas to flow into the actuator 12.
As the gas fills the actuator 12, pressure builds against the diaphragm 24 forcing the diaphragm 24 away from the sealing cup 38, thereby exposing the opening 44. The gas therefore flows through the opening 44 in the diaphragm 24 and toward the release valve 42. The release valve 42 includes a valve plug 46 and a release spring 54 biasing the valve plug 46 into a closed position, which is depicted in FIG. 1. Upon the pressure within the actuator 12 and adjacent the release valve 42 reaching a predetermined threshold pressure, the valve plug 46 displaces upward against the bias of the release spring 54 and opens, thereby exhausting gas into the atmosphere and reducing the pressure in the regulator 10.
When selecting a valve port for use in a particular application, technicians are charged with the task of maximizing flow capacity at the set control pressure while minimizing the amount of “droop.” Typically, this is accomplished by selecting a valve port that affords some compromise between these competing interests. However, as mentioned above, these conventional valve ports only vary in orifice diameter and have constant seat heights. Therefore, while some conventional valve ports may function generally efficiently, other valve ports having different orifice diameters may not. Accordingly, the flow characteristics, and more particularly, the “boost” characteristics of the regulator 10 may not be optimized for every valve port.